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Ru<sup>II</sup> complexes of 1,2,3-triazole appended tertiary phosphines, [P(Ph){(o-C<inf>6</inf>H<inf>4</inf>)(1,2,3-N<inf>3</inf>C(Ph)CH}<inf>2</inf>] and [P(Ph){o-C<inf>6</inf>H<inf>4</inf>(CCH)-(1,2,3-N<inf>3</inf>-Ph)}<inf>2</inf>]: highly active catalysts for transfer hydrogenation of carbonyl/nitro compounds and for α-alkylation of ketones
Journal
Dalton Transactions
ISSN
14779226
Date Issued
2022-04-06
Author(s)
Namdeo, Pavan K.
Sheokand, Sonu
Kote, Basvaraj S.
Radhakrishna, Latchupatula
Kunchur, Harish S.
Saini, Prateek
Ramakrishnan, Srinivasan
Balakrishna, Maravanji S.
Abstract
The synthesis of two new 1,2,3-triazole appended monophosphines [P(Ph){(o-C6H4)(1,2,3-N3C(Ph)CH}2] (1) and [P(Ph){o-C6H4(CCH)(1,2,3-N3-Ph)}2] (2) and their RuII complexes is described. The reactions of 1 and 2 with [Ru(PPh3)3Cl2] in a 1 : 1 molar ratio produced cationic complexes 3 and 4, respectively. Both the complexes showed very high catalytic activity towards transfer hydrogenation, nitro reduction, and α-alkylation reactions and afforded the corresponding products in good to excellent yields. The free energy of β-hydride elimination from the respective Ru-alkoxide intermediates, a key mechanistic step common to all the three catalytic pathways, was calculated to be close to ergoneutral by density functional theory-based calculations, which is posited to rationalize the catalytic activity of 3. The reduction of aromatic nitro compounds was found to be highly chemoselective and produced the corresponding amines as major products even in the presence of a carbonyl group. The triazolyl-N2 coordinated RuII-NPN complex 3 showed better catalytic activity compared to the triazolyl-N3 coordinated complex 4.
Volume
51